Ever since I got this ex-SpeedSource car it has been somewhat difficult to crank. I hear other cars crank right up like a street car but this one doesn't. Now I can't get it to start.

I have changed the starter, charged the battery, and have it on a battery booster pushing 22+ volts but it turns over very slowly. (I'll worry about firing later but I'd like to get this issue behind me.) Probably 120 rpm. Often it will get slower and slower. It is not battery posts because I get >12 volts in the wire inside the cables. Can the engine itself or flywheel do this? Makes no difference if in neutral w/ clutch in or out.